Influence of phomopsin and ivalin on steroid‐hormone binding and growth of mcf‐7 human breast cancer cells

Abstract

Ivalin is a plant alkaloid that inhibits the induction of tumors in animals. Phomopsin is a mycotoxin known to be carcinogenic. To determine if these compounds influence endocrine responsiveness, their effect on steroid receptors was measured. Neither of these toxins had a direct effect on either the binding capacity or the rate of steroid association of [3H]estradiol‐17ß, [3H]R5020, or [3H]dexamethasone to their respective receptors in cytosol of human breast cancer and rat liver. However, steroid receptor levels of MCF‐7 cells, grown in tissue culture, were altered by ivalin and phomopsin. Ivalin at 10–6 M depressed estrogen receptor levels, while glucocorticoid receptor levels were increased. At 10–6 M, phomopsin was inhibitory of both progestin and glucocorticoid binding capacities. Data obtained from the proliferation of MCF‐7 cells indicated that ivalin and phomopsin at 10–6 M decreased the number of cells grown in tissue culture. Phomopsin exhibited an inhibitory effect on both [3H] thymidine and [3H]glycine incorporation, while ivalin stimulated [3H]glycine incorporation.